[LLVMbugs] [Bug 15212] New: Clang handles __builtin_object_size in wrong way

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15212

            Bug ID: 15212
           Summary: Clang handles __builtin_object_size in wrong way
           Product: clang
           Version: 3.2
          Hardware: PC
                OS: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: ili.filippov at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

__builtin_object_size (void * ptr, int type) returns a constant number of bytes
from ptr to the end of the object ptr pointer points to.
But if type == 1 it understands object as the nearest surrounding of ptr and if
type == 0 it understands object as the whole object, contains the object
ptr points to.

If we write simple example:
#include <stdio.h>
struct a
{
    int t[10];
};

int main()
{
    a t[10];
    printf("%d\n",__builtin_object_size(&t[0].t[0],0));
    return 0;
}
Clang will answer 400 and it is right, because it is 4*10*10
But if we changed
printf("%d\n",__builtin_object_size(&t[0].t[0],0));
to
printf("%d\n",__builtin_object_size(&t[0].t[0],1));
Clang will also answer 400 and it is wrong, because the size of t.t is only 40
(10*4).




--
Software Engineer
Intel Compiler Team
Intel Corp.

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